Magnetic sensing devices have many applications, including navigation, position sensing, current sensing, vehicle detection, and rotational displacement. There are many types of magnetic sensors, but essentially they all provide at least one output signal that represents the magnetic field sensed by the device. The Earth, magnets, and electrical currents can all generate magnetic fields. The sensor may be able to detect the presence, the strength, and/or the direction of the magnetic field. The strength of the magnetic field may be represented by a magnitude and a polarity (positive or negative). The direction of the magnetic field may be described by its angular position with respect to the sensor. One of the benefits of using magnetic sensors is that the output of the sensor is generated without the use of contacts. This is a benefit because over time contacts can degrade and cause system failures.
A Hall sensor is a type of magnetic sensor that uses the Hall Effect to detect a magnetic field. The Hall Effect occurs when a current-carrying conductor is placed into a magnetic field. A voltage is generated perpendicular to both the current and the field. The voltage is proportional to the strength of the magnetic field to which it is exposed. The current-carrying conductor is called a Hall element and it is typically composed of a semiconductor material.
One of the first practical applications of the Hall Effect was as a microwave power sensor in the 1950s. With the later development of the semiconductor industry and its increased ability for mass production, it became feasible to use Hall Effect components in high volume products. In 1968, Honeywell's MICRO SWITCH division produced a solid-state keyboard using the Hall Effect. The Hall Effect sensing element and its associated electronic circuit are often combined in a single integrated circuit.
In its simplest form, a Hall element can be constructed from a thin sheet of conductive material with output connections perpendicular to the direction of electrical current flow. When subjected to a magnetic field, the Hall Effect element responds with an output voltage that is proportional to the magnetic field strength. The combination of a Hall Effect element in association with its associated signal conditioning and amplifying electronics is sometimes called a Hall Effect transducer. Such Hall elements are typically implemented in the context of a Hall component or device such as a Hall chip.